1. Field of the Invention
This invention relates broadly to medico-surgical tube devices for monitoring intraesophageal pressure in a patient.
More particularly, it concerns an improved form of nasogastric tube provided with an esophageal balloon cuff and fluid conduction means permitting esophageal pressure to be monitored to determine lung compliance and respiratory work values in patients.
2. Description of the Prior Art
The use of esophageal balloons to measure intrapleural pressure in the study of lung mechanics was introduced in 1949 by Buytendijk. The technique employs an air-containing balloon sealed over a catheter which transmits balloon pressure to a low compliance manometer or pressure transducer. The catheter is usually intubated through a nare and positioned in the lower or middle third of the esophagus [J. Appl. Physiol. 14:525 (1959) and 19(2):207-211 (1964)].
Numerous studies have compared intrapleural pressures with those in the esophagus noting the differences and similarities under a variety of conditions in both normal and abnormal subjects [J. Lab. Clin. Med. 40:664 (1952) and 40:674-681 (1952)]. The results of these studies have shown that changes in intraesophageal pressure closely approximate changes in intrapleural pressure, but that absolute (gauge) pressures in the esophagus tend to be more positive than those in the pleural cavity, particularly when measurements are conducted in the supine position. Techniques for improving absolute pressure measurements have been described by several investigators [J. Appl. Physiol. 19(2):207-211 (1964); 29:283-287 (1970) and 37(4):600-603 (1974)]. The discrepancy between absolute pressures measured in the esophagus and pleural cavity, however, has not curtailed investigation of the mechanics of ventilation since pressure changes are of much greater significance than absolute pressures. Innumerable investigators have utilized esophageal balloons to characterize the mechanical properties of the lung in both health [J. Appl. Physiol. 5:779 ( 1953) and 38(3):411-417 (1975)], and in disease [J. Appl. Physiol. 23:433-438 (1967) and 26:330 (1969)] as well as in determining the work of breathing [Ann. Surg. 171(5):679-685 (1970)].
Despite the extensive volume of literature demonstrating acceptance and use of the esophageal balloon as a research and laboratory tool, there are few reports of its use as a monitoring tool in the clinical management of acutely ill patients [Surgery 70(2):280-287 (1971) and Am. J. Surg. 124:262-269 (1972)]. This limited use in the clinical environment has been due primarily to time consuming technical difficulties inherent in current procedures. In order to obtain the necessary serial or trend information concerning a patient's intrapleural pressure, the health care team has had to perform repeated esophageal intubations or make provisions for maintaining a double intubation of the esophagus, namely, an esophageal balloon catheter and a nasogastric tube.
In the clinical management of patients, it has been found that patients with respiratory problems, or that have a risk of developing such problems, frequently require nasogastric tubes. Also, nearly all patients requiring mechanical ventilation have nasogastric intubations as part of their routine clinical management. Hence, there exists a need for a nasogastric tube that can perform the additional function of allowing continuous or serial monitoring of esophageal pressure.
Aside from the field of esophageal catheter research, it is known to provide nasogastric tubes with a plurality of lumen, one of which may communicate with an inflation balloon on the catheter proximal of the distal end (U.S. Pat. Nos. 3,046,988 and 3,055,371). It is also known to use the balloon cuff on a catheter to measure pressures within a subject's body cavity during diagnostic procedure using the catheter (French Pat. No. 790,091). Also, multiple-lumen balloon-cuff catheters have been used for pressure measurement other than via the balloon-cuff (U.S. Pat. No. 3,448,739).